The Server Time Protocol feature is designed to provide the capability for multiple servers and Coupling Facilities to maintain time synchronization with each other, without requiring a Sysplex Timer. The servers and Coupling Facilities that are capable of supporting Server Time Protocol are the z890, z990, and later servers.

Server Time Protocol is a server-wide facility that is implemented in the Licensed Internal Code (LIC) and presents a single view of time to Processor Resource/Systems Manager™ (PR/SM™). STP uses a message-based protocol in which timekeeping information is passed over externally defined Coupling Links - InterSystem Channel-3 (ISC-3) links configured in peer mode, Integrated Cluster Bus-3 (ICB-3) links, Integrated Cluster Bus-4 (ICB-4) links. and Parallel Sysplex InfiniBand (PSIFB) links. These can be the same links that already are being used in a Parallel Sysplex for Coupling Facility (CF) message communication.

By using the same links to exchange timekeeping information and Coupling Facility messages in a Parallel Sysplex, STP can scale with distance. Servers exchanging messages over short distance links such as ICB-3 and ICB-4 are designed to meet more stringent synchronization requirements than servers exchanging messages over long distance links such as ISC-3 (distances up to 100 km, longer distances possible with RPQ 8P2263), where the synchronization requirements are less stringent. This is an enhancement over the current Sysplex Timer implementation, which does not scale with distance.

The STP design has introduced a new concept called Coordinated Timing Network (CTN). A Coordinated Timing Network (CTN) is a collection of servers and Coupling Facilities that are time synchronized to a time value called Coordinated Server Time.

STP supports the following functions:

Please see the STP Hardware announcement 106-715 Server Time Protocol for IBM System z9, zSeries 990 and 890; non-raised-floor support for System z9 BC dated October 10, 2006 or download (PDF, 67KB) the pdf version.

STP FAQs can be seen at:

STP Summary

The Server Timer Protocol feature is designed to simplify hardware configurations by:

Additional value from Server Time Protocol may be obtained by:

Concurrent Migration and Coexistence

STP introduces the concept of a Coordinated Timing Network (CTN), to meet two key goals of System z customers:

A CTN can be configured in two ways:

A Mixed CTN allows you to meet the above requirements of concurrent migration and coexistence. The coexistence allows for a sysplex configuration where members of the sysplex may reside on a z800 or z900 server.

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